Environmental health: addition of sound levels: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

PSM · Environmental health: addition of sound levels

Sample item

Two identical machines each produce 90 dB at the operator's position. What is the expected sound level when both run together?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. About 93 dB

The decibel scale is logarithmic, so sound levels cannot be added arithmetically. Doubling the sound intensity adds 10 log 2, about 3 dB, giving 93 dB. This is why a small rise in decibel level represents a large rise in sound energy.

Option by option

  • A. 90 dB

    Two sources produce more sound energy than one, so the level cannot remain 90 dB.

  • B. 180 dB

    Adding the decibel values directly ignores the logarithmic scale.

  • C. About 93 dB (correct)

    Correct. Doubling the sound energy adds about 3 dB.

  • D. About 96 dB

    A rise of 6 dB would need roughly four times the intensity.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, About 93 dB. The decibel scale is logarithmic, so sound levels cannot be added arithmetically.

Why is "90 dB" not the answer?

Two sources produce more sound energy than one, so the level cannot remain 90 dB.

Why is "180 dB" not the answer?

Adding the decibel values directly ignores the logarithmic scale.

Why is "About 96 dB" not the answer?

A rise of 6 dB would need roughly four times the intensity.

What concept does this question test?

It tests Environmental health: addition of sound levels in PSM. Doubling the sound intensity adds 10 log 2, about 3 dB, giving 93 dB. This is why a small rise in decibel level represents a large rise in sound energy.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Environmental health: addition of sound levels?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.